Adhesive processes



Oct. 18, 1966 Y J. M. NARDONE 3,278,960

ADHESIVE PROCESSES Filed March 26, 1963 Inventor IB/ n M Naraone By his Azorney United States Patent 3,278,960 ADHESIVE PROCESSES John M. Nardone, Wakefield, Mass, assignor to United Shoe Machinery Corporation, Boston, Mass., a corporation of New Jersey Filed Mar. 26, 1963, Ser. No. 268,137 Claims. (Cl. 12-442) This application relates to an adhesive process for the attachment of soles to shoe uppers.

Sole attaching by a procedure involving depositing molten polymeric resin adhesive as a ribbon adhered on attaching marginal areas of a sole and thereafter heating the deposited ribbon of adhesive and underlying sole material and concurrently heating the attaching portions of a bottom of a shoe upper, has been found to present marked advantages over earlier procedures involving the use of solvent adhesive applied both to the sole and to the bottom of a shoe upper.

The development of a strong bond by the polymer resin adhesive is dependent in considerable measure on the successful penetration and/ or thorough wetting of the surface portion. Because of irregularities in the roughed surface of the outsole and of the bottom of the upper due, for example to pleating at the toe and to tacks or other holding devices, it has been necessary to use at least a minimum thickness for the ribbon and some difliculty has been encountered in the sole attaching pressing operation. That is, the molten adhesive has allowed skidding of the outsole relative to the shoe upper by a lubricating action. Also in the course of pressing, some difliculty has been encountered due to squeeze out of molten adhesive from between the outsole and shoe upper.

It is an object of the present invention to provide an adhesive sole attaching process in which the difiiculties of skidding and squeeze out are reduced.

To this end and in accordance with a feature of the present invention, thick deposits of molten adhesive are laid down in spaced areas on the attaching marginal portions of an outsole with intervening areas providing spaces to receive molten adhesive from the thick deposits in subsequent assembly and pressing steps of sole attaching. The spaced areas are preferably in the form of lines of substantial thickness and narrow width. The outsole with the spaced areas such as lines of adhesive is subjected to heat, ordinarily radiant heat, to soften the adhesive and to prepare the outsole areas for permanent adhesive union with the adhesive. The bottom of the shoe upper is also heated and is assembled against the heated sole. The character of softening of the thick deposits of adhesive and the availability of uncoated or very thinly coated outsole areas between the thick deposits to receive adhesive from the thick deposits markedly reduces the skidding action of an outsole relative to the shoe upper. When the outsole and shoe upper are strongly pressed together, the softened adhesive is forced into wetting and/ or penetrating engagement with the shoe upper and is spread over into the portions of the outsole between the thick deposits. The reduced quantity of adhesive present in the spaced areas as contrasted with the quantity of adhesive in a continuous ribbon enables establishment of a bond with a very short holding time after the sole and shoe upper have been forced together so that pressure may be released promptly.

The invention will be described further in connection with the attached drawings forming part of the disclosure in the present case in which:

FIG. 1 is a diagrammatic angular view with parts broken away of a modified outsole cementer laying down spaced lines of adhesive on the attaching margin of an outsole;

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FIG. 2 is an enlarged diagrammatic angular view with parts broken away of the extrusion nozzle portion of the outsole cementer showing the laying down of extruded adhesive strands to form the spaced adhesive lines on the attaching margin of an outsole;

FIG. 3 is a diagrammatic elevational view showing heating of the adhesive lines and outsole and the heating of the bottom of a shoe upper; and

FIG. 4 is a diagrammatic elevational view showing the bonding of an outsole to an upper in a sole attaching press.

The present process involves as a first step the laying down on the attaching marginal surface of an outsole of spaced deposits, usually lines of thermoplastic adhesive of which the uppermost portions project above the surface of the outsole. It is preferred that the lines of adhesive have a cross section in which the dimension taken perpendicular to the outsole surface is at least about onethird of the dimension parallel to the outsole surface.

The thickness and spacing of the deposits of adhesive are interdependent. That is, the intervening areas provide space between the sole and the desired level, 0.010 inch, of adhesive above the sole at least about equal to that portion of the volume of adhesive in the thick deposits which is above the desired level of 0.010 inch. If the deposits are relatively close together then the thickness will be less than with more widely spaced deposits. The thickness of such deposits from crest to sole surface may be as little as about 0.015 inch; but with the preferred spaced line application of adhesive, a thickness of from 0.025 inch to 0.060 inch preferably 0.03 to 0.05 inch with a spacing at least. 0.025 inch and preferably from two to four times the thickness is effective.

When an outsole provided with spaced adhesive deposits of substantial thickness is heated as by radiant heat the portions of the adhesive deposits receiving heat most directly from the heat source are softened more than portions less directly heated. For example, in a line of adhesive the portions of the adhesive line farthest from the sole are the hottest and most fluid and portions closer to the sole are more viscous. When a sole carrying such adhesive lines so heated is assembled and pressed against an upper, the most fluid portions of the adhesive are held by the less fluid portions in position for wetting or penetrating surface portions of the bottom of the shoe upper against which the outsole is pressed. Thus, the most fluid portion of the adhesive is in the most favorable position for entering into adhesive engagement with the bottom of the shoe upper. Further pressure effects spreading of the adhesive lines so that the fluid adhesive flows over to the heated surface portions between the lines and will establish adhesive engagement between the upper and substantially the entire area of the outsole under and between the adhesive lines. By reason of the flow of the adhesive under pressure which has an effect in orienting and aiding in inducing crystallization of a crystallizable resin polymer adhesive and by reason of the smaller ultimate thickness of the adhesive layer after assembly and pressure, a very strong and very rapidly setting adhesive bond is estab lished between an outsole and an upper.

An auxiliary advantage of the spaced areas of adhesive is that in spotting, i.e., the initial positioning of the outsole relative to the upper, skidding of the outsole relative to the upper is largely avoided by reason of the more viscous base portion-s of the adhesive areas which resist movement after the softer upper portions of the adhesive lines are wiped into the intervening spaces by relative movement of the outsole to the shoe upper.

Deposition of spaced areas of thermoplastic adhesive in the desired relationship is most effectively provided by extruding separate strands of molten adhesive through orifices adjacent or spaced slightly from the surface of an outsole moved relative thereto. In this relation there is no fluid pressure tending to spread the adhesive and flatten the adhesive lines on the surface of the outsole. The extruded adhesive is merely laid on the outsole surface so that, for example an adhesive strand extruded from a round orifice may be flattened only slightly to an oval cross section adhering to the outsole at its line of contact with the outsole. It has been found that, since'adhesive is extruded at a uniform rate from each of the orifices of the nozzle, hollows or ridges in the outsole surface do not interfere'with uniform deposition of adhesive. inside of the various curves and hence are shorter than the outside lines, the innermost lines will be thicker than the outside lines. This provides the further advantage that additional adhesive is available for bonding at a distance from the sole edge where it is not subject to squeeze out. Comparable but somewhat less satisfactory adhesive application is obtainable where the adhesive is extruded through an applying device in which the molten adhesive is confined between the outsole and forming portions of the nozzle; but the cross section of adhesive line thus achieved is not as satisfactory as that achieved by the preferred procedure. 7

To aid in understanding the operation of the invention, the process of cement outsole attaching will' be described as it is practiced using one form of cement applying'apparatus. Spaced lines 10 of molten thermoplastic adhesive are spread on the attaching margin 12 of an outsole 14 by a modified outsole cementer 16, as shown in FIG. 1. The outsole cementer 16 comprises a nozzle 18 for extruding and laying down the lines 10 of adhesive, a drive wheel 20 for moving the outsole 14 at a desired rate past the nozzle 18, and a guide 22 for maintaining the margin 12 of the outsole 14 in desired relation to the nozzle 18. As best shown in FIG. 2, the nozzle 18 has spaced extrusion orifices 24 the lower edges of the' orifices being supported adjacent the surface of the outsole by a portion 26 of the nozzle which rides on the outsole surface. The molten adhesive strands leaving the orifices 24 are laid down on the outsole surface as oval cross section lines at least lightly adherent to the outsole surface. In the device shown, molten cement for the nozzle 18 is supplied from a melting device 28 for handling a rod or strand 30 of thermoplastic adhesive; but it is to be understood that other molten adhesive supplies may be used where the nature of the adhesive permits.

As shown in FIG. 1, the cementer 16 appliesspaced lines 10 extending around at least the forward portion of the outsole 14. These lines may extend around the entire margin of the outsole depending on the shoe construction involved. The deposited lines 10 of adhesive may be of the order of about 0.025 to about 0.06 inch, preferably 0.03 to 0.05 inch in thickness and from 0.025 to 0.10 inch in width. It is desirable that the spaces be at least equal to the thickness of the lines and preferably from two to four times the thickness. The present solventfree lines of adhesive contain significantly smaller quantities of adhesive than the continuous bands but present the adhesive in most advantageous relation to the outsole for forming a strong bond to an upper.

The molten adhesive lines 10 applied to the sole cool and solidify rapidly due to the temperature and heat capacity of the sole material so that ordinarily only minor or superficial penetration of a leather outsole oc curs, and substantially the entire volume of adhesive remains upstanding as lines 10 on the surface of the outsole 14. It has been found that the applied adhesive lines 10 are usually only lightly adherent and are strippable as a self-supporting filament, i.e., are provisionally attached so that in the event of a malfunction of the device or of, some other factor, the adhesive lines 10 may be readily removed and the outsole 14 given a second treatment to provide the desired adhesive lines. The

Also since the innermost lines are at the.

outsoles 14 may be stacked substantially immediately after application of the adhesive because of the rapid solidification of the adhesive.

The thermoplastic adhesive useful for outsole attaching according to the present method, involves a special combination of physical characteristics for effective operation. In general, the adhesive must be thermoplastic at least to the extent that it does become infusible prior to completion of the two heating operations involved in the present process. Resins which have been found useful include the polyesters from reaction of dicarboxylic acids and glycols, polyesteramides, for example adipic polyesteramides in which the hydroxy component is 1,6 hexanediol, 1,4 .butanediol or ethylene glycol, stereospecific catalyzed polymers of vinyl alkyl ethers where the alkyl group has from 1 to 4 carbon atoms, polymers and copolymers of lower alkyl acrylates and methacrylates. Resins having molecular weights preferably not over about 50,000 have been preferred in order that they may have the necessary fluidity for spreading, wetting and penetration. Mixtures of polymeric materials having molecular weights above this value, with resins of lower molecular weight may be compounded to approximate the physical properties of the preferred resins for use in the present process. It has been found'desirable that the adhesive having a relatively wide temperature range, preferably a range of at least 20 C. in which it is viscoelastic when cooled from molten condition. The term visco-elastic refers to a condition in which the adhesive.

is somewhat rubbery but deformable and flowable under pressure, in order that it may permit limited movement, for example of the outsole 14 relative to an upper 32 so that accurate positioning of the outsole 14 relative to the upper 32 may be assured even after the outsole has come in contact. visco-elastic vcondition in the preferred adhesives occurs may be from about 10 C. to about 60 C. below the melting point of the adhesive; and the adhesive will harden to a strong, tough condition at temperatures at.

least as high as 50 C. Other important properties are relatively high strength, toughness and at least limited flexibility at room temperature in order that the adhesive may successfully withstand the severe stresses encountered in the use of a shoe.

A useful class of adhesives is that of the polyesters, for

example, terephthalates isophthalates, sebacates, succin-y ates, etc. Preferred polyesters include condensates of a lower alkylene glycol such as ethylene glycol or butylene glycol with dicarboxylic acids, for example, condensates.

of 1,4 butane diol with mixed terephthalate and isophthalate components in the molar ratio of from about 1:1 to about 4:1 and condensates'of mixed ethylene glycol and 1,4 butane diol and mixtures of these with mixed terephthalate, isophthalate and sebacate components in percent ages of 40% to 60% terephthalate, 20% to 50% isoph 32 on a rack 34 spaced from the radiant heating unit 36 employed for action on the outside 14 as shown in FIG. 3.

The outsole 14 is positoned on a rack 38 relative to the 1 radiant heating unit 36 so'that the radiant heat falls on the adhesive lines 10 and the surfaces of the outsole adjacent the lines 10. The lines 10 of adhesive are softened by the radiant heat with the upper portions of the lineswhich receive heat most directly being made more fluid than portions of the lines closer to the outsole surface.

The temperature range in which the Heat is also absorbed by the outsole material adjacent the adhesive lines to prepare the outsole surface for permament adhesive engagement by molten adhesive. It has been found that the adherence of the lines to the outsole surface is important since it holds the adhesive lines in extended condition and does not allow the beading up through surface tension of adhesive merely laid on a surface.

After heating of the sole attaching surface 31 of the shoe upper 32 and radiant heating of the lines of adhesive and portions of the outsole 14 adjacent the lines, the outsole 14 is positioned on the bottom 31 of the shoe upper 32. The adhesive in the lines 10 although somewhat rubbery in heated condition, has a visco-elastic nature which allows some sliding of the outsole 14 relative to the shoe upper 32; but the sliding is limited in extent.

After positioning of the outsole on the bottom of the shoe upper, the assembled shoe upper 32 and outsole 14 are placed in a sole attaching press 40 (see FIG. 4) and subjected to sole attaching pressure. Surprisingly, notwithstanding the amount of time which is available for assembling of the out-sole and upper, pressure in the sole attaching press 40 may be released in a matter of only a few seconds. The ability of the adhesive to hold the outsole 14 firmly on the shoe upper 32 after so short a time is due in some measure to the fact that the deeply heated outsole portions permit excellent penetration of the molten adhesive, i.e., do not chill penetrating portions of the adhesive to constitute a block against further penetration. This excellent pentration and/ or wetting of the outsole and shoe upper by the adhesive reduce the thickness of the adhesive between outsole and upper and when sole attaching pressure is applied create a geometry between the outsole and shoe upper in which the adhesive may function most effectively.

A further factor which is particularly valuable in the bonding of plasticized vinyl resin soles is that the deep heating of the out-sole and upper create a condition in which resins such as polyesters may at least partially crystallize. Onset of crystallation is aided by the flow involved in spreading of the adhesive lines 10 onto adjacent areas of the outsole. The crystallized resin adhesives are less soluble in plasticizers and hence the adhesive lines are less subject to weakening by plasticizer from vinyl resin soles.

The above explanation of the desirable action of the adhesive is given as of possible assistance in understanding the invention; but it is to be understood that patentability is not based on the correctness of the theory advanced.

The process has been described as it applies to the bonding of a leather outsole to a shoe upper using a single layer of adhesive. In some relations, for example with some commencial, natural or synthetic rubber outsole materials, it has been found desirable to provide a primer coat on the attaching surface of the outsole to improve the union between the thermoplastic adhesive and the outsole. It is to be remembered, however, that even Where such a primer is indicated, many of the advantages of the present process are still secured, since it is not necessary to apply adhesive to the bottom of the shoe upper and the danger of contamination of portions of the shoe upper which will be exposed in use is avoided since the adhesive for sole attaching is only on the outsole.

Primers for natural or synthetic rubber outsoles may be, for example a solution of chlorinated rubber in a volatile organic solvent or maybe a relatively stable polyisocyannate, for example a polyarylene polyisocyanate, commercially available as PAPI.

The following examples are given for assistance in understanding the invention. The invention is not restricted to the particular materials, proportions or procedural conditions employed in the examples.

6 Example I A polyester was prepared by the reaction and condensation of 1,4 butane diol and equimolar proportions of dimethyl terephthalate and isophthalic acid. Condensation was carried out to form a resinous material having a melting point of about 142 C. (ball and ring). This resin was formed into a flexible rod about /5. inch in thickness and the rod was fed to a melting device disposed to provide molten adhesive to an out-sole cementer. The nozzle of the cementer was provided with four orifices for extrusion of the molten resin adhesive, each orifice being 0.030 inch in diameter. The orifices were spaced about 0.10 inch apart. The melting device and cementer were adjusted to deliver molten resinous material through the nozzle to the surface of a leather outsole at a temperature of 350 F. The "lines of resin deposited on the outsole solidified promptly after deposition and were found to have a thickness of about .025 and a width of about .040 inch.

The leather outsole was disposed with the surface carrying the lines of resin adhesive towards a radiant heat source for 15 seconds. The radiant heat raised the surface temperature of the leather to about 150 to 175 F.; and raised the temperature of the lines of adhesive to an extent that the resin became fluid and Wet the surface of the leather.

At the same time the bottom of a shoe upper was exposed to radiant heat to raise the temperature of the attaching surface of the shoe upper to about to about F. The outsole was then spotted on the upper and the assembly placed in a sole attaching press. Pressure was applied to the extent of 200 to 225 lbs. total pressure on the assembly, and after ten seconds the pressure was removed. On examination it was found that the sole was strongly attached to the shoe upper, that the edges of the sole were very tight to the upper and that there had been no squeeze-out of adhesive.

Example II A polyester was prepared by the reaction and condensation of ethylene glycol with a mixture comprising in terms of mol percentages 60% of dimethyl terephthalate, 20% isophthalic acid and 20% sebacic acid. Condensation was carried out to the extent of providing a melting point of C. (ring and ball). This resin was formed into a rod and used for attaching leather soles to shoe uppers, using the procedure and conditions set forth in Example I but delivering the molten resinous material at a temperature of about 375 F. The sole was found to be strongly and tightly attached to the shoe upper.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. The process of permanently attaching a shoe sole and a shoe bottom which comprises laying down molten substantially solvent-free thermoplastic synthetic polymeric resin adhesive at least 0.015 inch thick in spaced areas on marginal sole attaching surface portions of a sole, with intervening areas providing space between said marginal surface portions and a level of 0.010 inch above said surface portions at least about equal to the volume of adhesive above the level of 0.010 inch, thereafter cooling the deposited adhesive to solid condition at least lightly adhered to the sole, subsequently subjecting said adhesive and sole to radiant heat to restore the adhesive to molten condition and to prepare the sole area for permanent adhesive attachment, heating the bottom portion of the shoe to which the sole is to be attached, then bringing the heated shoe bottom and sole together with the molten adhesive between them, exerting pressure to force the adhesive into permanent attaching relation with the heated surfaces of both the sole and shoe bottom, and finally cooling the adhesive to establish rapidly a strong union of the sole and the shoe.

2. The process of permanently attaching a shoe sole and a shoe bottom which comprises laying down molten marginal surface portions and a level of 0.010 inch above said surface portions at least about equal to the volume of adhesive above the level of 0.010 inch, thereafter coolattached, then bringing the shoe bottom and outsole ,to-

ing the adhesive to solid condition at least lightly adhered to the sole, said resin having a melting point in the range of from about 80 C. to about 300 C. and said adhesive hardening to a strong tough condition at temperatures of at least 50 C., subsequently subjecting said adhesive and sole to radiant heat to restore the adhesive to molten condition and to prepare the sole area for permanent adhesive attachment, heating the bottom portion of the shoe to which the sole is to be attached, then bringing the heated shoe bottom and sole together with the molten adhesive between them, exerting pressure to force the adhesive into permanent attaching relation with the heated surfaces of both the sole and shoe bottom, and finally cooling the adhesive to establish rapidly a strong union of the sole and the shoe.

3. The process of permanently attaching a shoe sole and a shoe bottom which comprises forming spaced lines of substantially solvent-free thermoplastic synthetic polymeric resin adhesive from .025 to .06 inch in thickness, adhered to marginal attaching surface portions of the sole, intervening areas between said lines providing space between said marginal surface portions and a level of 0.010 inch above said surface portions at least about equal to the volume of adhesive above the level of 0.010 inch, subsequently subjecting said adhesive and sole to radiant heat to melt the adhesive and to prepare the sole area for permanent adhesive'attachment, concurrently heating the bottom portion of the shoe to which the sole is to be attached, then bringing the shoe bottom and sole together with the lines of molten adhesive between them and exerting pressure to force the adhesive into permanent attaching relation with the heated surfaces of both the sole and shoe bottom, and finally cooling the adhesive to establish rapidly a strong union of the sole and the shoe.

4. The process of permanently attaching a shoe sole and a shoe bottom which comprises forming spaced lines of substantially solvent-free thermoplastic synthetic polymeric resin adhesive from .025 to .06 inch in thickness, by extruding the adhesive in molten condition and laying down the extruded adhesive on marginal attaching surface portions of the sole and thereafter cooling the adhesive to form self-supporting adhesive lines carried by and at least lightly adhered to the outsole surface, intervening areas between said lines providing space between marginal surface portions and a level of 0.010 inch above said surface portions at least about equal to the volume of adhesive above the level of 0.010 inch, subsequently subjecting said adhesive and sole to radiant'heat to restor the adhesive to molten condition and to prepare thesole area for permanent adhesive attachment, concurrently heating the bottom portion of the shoe to which the sole is to be gether with the lines of 'molten adhesive between them and exterting pressure to force the adhesive into permanent attaching relation with the heated surfaces of both the sole and shoe bottom, and finally cooling the adhesive to establish rapidly a strong union of the sole and the shoe. 5

5. The process of permanently attaching a shoe sole and a shoe bottom which comprises forming spaced lines of substantially solvent-free thermoplastic synthetic polymeric resin adhesive from .025 to .06 inch in thickness, from .025 to .1 inch in width a distance from two to four times the thickness of said lines by extruding separate strands of the adhesive in molten condition and laying down the extruded adhesive strands on marginal attaching surface portions of the sole and thereafter cooling the adhesive to form self-supporting adhesive lines carried by and at least lightly adhered to the outsole surface, intervening areas between said lines providing space between marginal surface portions and a level of 0.010'inch above said surface portions at least about equal to the volume of adhesive above the level of 0.010 inch, said resin having a melting point in the range of from. about C. to about 300 C. and said adhesive: hardening to a strong tough condition at temperatures of at least 50 C., subsequently subjecting said adhesive and sole to radiant heat to restore the adhesive to molten condition and to prepare the sole area for permanent adhesive attachment, concurrently heating the bottom portion of the shoe .to which the sole is to be attached, then bringing the shoe bottom'and outsole together with the lines of molten adhesive between them and exerting pressure to forcethe adhesive into permanent attaching relation with the heated surfaces of both the sole and shoe bottom, and finally cooling the adhesive to establish'rapidly a strong union of the sole and the shoe.

References Cited by the Examiner UNITED STATES PATENTS 2,385,523 9/1945 Marasco 12142 2,648,078 8/ 1953 Eppler. 3,021,543 2/1962 Crowley 12-142 3,056,984 10/1962 Snitzer 12142 3,168,754 2/1965 Rossitto 12-142 JORDAN FRANKLIN, Primary Examiner. PATRICK D. LAWSON, Examiner. 

1. THE PROCESS OF PERMANENTLY ATTACHING A SHOE SOLE AND A SHOE BOTTOM WHICH COMPRISES LAYING DOWN MOLTEN SUBSTANTIALLY SOLVENT-FREE THERMOPLASTIC SYNTHETIC POLYMERIC RESIN ADHESIVE AT LEAST 0.015 INCH THICK IN SPACED AREAS ON MARGINAL SOLE ATTACHING SURFACE PORTIONS OF A SOLE, WITH INTERVENING AREAS PROVIDING SPACE BETWEEN SAID MARGINAL SURFACE PORTIONS AND A LEVEL OF 0.010 INCH ABOVE SAID SURFACE PORTIONS AT LEAST ABOUT EQUAL TO THE VOLUME OF ADHESIVE ABOVE THE LEVEL OF 0.010 INCH, THEREAFTER COOLING THE DEPOSITED ADHESIVE TO SOLID CONDITION AT LEAST LIGHTLY ADHERED TO THE SOLE, SUSBSEQUENTLY SUBJECTING SAID ADHESIVE AND SOLE TO RADIANT HEAT TO RESTORE THE ADHESIVE TO MOLTEN CONDITION AND TO PREPARE THE SOLE AREA FOR PERMANENT ADHESIVE ATTACHMENT, HEATING THE BOTTOM PORTION OF THE SHOE TO WHICH THE SOLE IS TO BE ATTACHED, THEN BRINGING THE HEATED SHOE BOTTOM AND SOLE TOGETHER WITH THE MOLTEN ADHESIVE BETWEEN THEM, EXERTING PRESSURE TO FORCE THE ADHESIVE INTO PERMANENT ATTACHING RELATION WITH THE HEATED SURFACES OF BOTH THE SOLE AND SHOE BOTTOM, STRONG UNION OF THE SOLE AND THE SHOE. 